The celebrity trainer went on an epic rant about the diet trend that’s sweeping Hollywood at the moment. In a video for Women’s Health, she said, “I don’t understand. Like, why would anyone think this is a good idea?”

“You know what we need to do? All fat and animal protein,” the former Biggest Loser trainer continued in a mocking voice, before laying down the law. “No! Bad plan. For a million reasons.”

Michaels, 44, who is known for her extremely tough but supportive training style and effective workout routines, went on to outline the reasons she thinks the high-fat, low-carb ketogenic diet — in which the goal is for the body to go into a state of ketosis to burn fat stores — is an unhealthy eating plan.

“Let’s start with the first [reason]: your cells. Your macromolecules are literally made up of protein, fat, carbohydrates, nucleic acids. When you do not eat one of the three macronutrients — those three things i just mentioned — you’re starving your cells,” she said. “Those macronutrients serve a very important purpose for your overall health and well-being. Each and every one of them. Period, end of story.”

Michaels, meanwhile, urges people to resist the temptation of any particular diet plan. “You don’t eat processed sugar, you don’t eat processed grains and to make a very long story short, avoid the keto diet,” she said at the conclusion of her rant. “Common sense: A balanced diet is key.”